1. Field of the Invention
The present invention relates to a vehicular display device in which a display background is blackfaced, and more particularly, to a vehicular display device in which a dial and a pointer are made to glow by the same light source.
2. Description of the Related Art
Display devices, that is, meters may take a digital form or an analog form. Though a digital meter is capable of displaying minute information values, there is much need for an analog meter.
An analog meter, as is well known, makes a rotating pointer point to characters, graduations or the like on a dial, and has flexibility in its means of display, for example, the pointer and the dial can be directly or indirectly illuminated in the night by a lamp, an EL or the like to allow a clear view of the pointer and the display on the dial.
The users of analog meters on board vehicles have required brightness more suited to see the meter and more easily readable designs, that is, improvement of visibility and readability, and the realization of a new-sense display as electronics technology has recently progressed.
Therefore, attempts to improve visibility and readability are made by blackfacing a display background through the use of a dark smoke filter as a front panel of a meter to make components other than a pointer, characters and graduations hard to see and simplify display design.
Furthermore, the pointer and characters or the like on the dial are made to glow and a high-contrast display is produced on the blackfaced display background, thereby achieving new-sense display as well as improving visibility and readability.
Pointers in such blackfaced meters are classified into a self-luminous type which itself functions as a light source, and a type which is made to glow by light from a light source.
The self-luminous pointer is formed itself by a cold-cathode tube shaped like a thin stick, or provided with many LEDs on the surface thereof.
In either case, the pointer needs high rotation torque because of its heavy weight, and it is expensive. This type of meter uses a cold-cathode tube for making a dial glow, and therefore, the cost of the meter itself is high.
In consideration of this point, a disk pointer has been suggested. In a disk pointer, a rotatable disk having a slit is located at an opening formed in the center of a dial, the slit is made to glow like a pointer by irradiating the disk from behind, and the dial is also made to glow by the back light. However, it is necessary to enlarge the disk itself in order to enlarge the pointer, and the pointer and characters on the dial cannot be overlapped.
The present applicant has suggested a disk pointer and a vehicular display device using the disk pointer in Japanese Patent Application No. 5-204909 which can solve the above problems.
The disk pointer and the vehicular display device will now be described with reference to the drawings.
FIGS. 12A, 12B and 12C are respectively perspective, exploded perspective and sectional views of a disk pointer 10.
Referring to these figures, the pointer 10 consists of a disk portion 20 and a pointer portion 30. A stand 21 is attached to the back center of the disk portion 20.
A light receiving opening portion 22 is formed from the center to a peripheral edge portion 20a of the disk portion 20. The opening portion 22 is shaped so as to open from behind the stand 21 to the peripheral edge portion 20a across the stand 21.
On the other hand, the pointer portion 30 consists of a light emitting portion 32 made of a plate member, and a light guide portion 34 formed to put the light emitting portion 32 therein.
The light guide portion 34 guides incident light to the light emitting portion 32, and is, as shown in the figures, provided with a conical cylinder portion 34a whose diameter increases from the center to the peripheral edge portion 20a of the disk portion 20 and a conical cylinder portion 34b whose diameter decreases as it extends outward from the peripheral edge portion 20a. Reflection treatment such as white melamine coating is applied on the inner surface of the light guide portion 34.
An opening portion 34a.sub.2 is formed on a bottom portion 34a.sub.1 of the conical cylinder portion 34a to correspond to the light receiving opening portion 22, and a slit 34c is formed on the upper surface of the light guide portion 34 along the longitudinal center line thereof. The light emitting portion 32 is fitted into the slit 34c.
In other words, the light guide portion 34 is shaped in agreement with the shape of the light receiving opening portion 22 between the center and the peripheral edge portion 20a of the disk portion 20, and the conical cylinder portion 34b having a tapered tip is formed outward from the peripheral edge portion 20a of the disk portion 20. This is for the purpose of improving the light-collecting power and preventing the occurrence of problems when the pointer 10 overlaps with characters on a dial.
Since the light guide portion 34 is thus shaped like a conical cylinder, it can easily reflect and guide light incident from a light source 15 through the opening portion 34a.sub.2 to the leading end thereof.
The light emitting portion 32 is made of a fluorescent acrylic plate. When the light emitting portion 32 is fitted in the slit 34c of the light guide portion 34, its upper end is nearly flush with the surface of the conical cylinder portion 34b of the light guide portion 32 outside the peripheral edge portion 20a of the disk portion 20, and projects like a dorsal fin from the surface of the conical cylinder portion 34a of the light guide portion 34 inside the peripheral edge portion 20a of the disk portion 20.
FIG. 13 is an exploded perspective view of an actual vehicular display device using the disk pointer 10.
Referring to FIG. 13, the display device comprises a movement 13 for driving the pointer 10, a conical reflector 14 having an opening portion 14a on the top thereof, a light source 15 made of a ring-shaped cold-cathode tube, a dial 16 with a hole 16a, having almost the same diameter as that of the pointer 10, in the center thereof, and a light leakproof ring 17 fitted in the hole 16a.
The light leakproof ring 17 has a center slot formed all around its circumference, thereby making the section thereof concave. The rim-like peripheral edge portion 20a of the disk portion 20 of the pointer 10 is just fitted in the concave portion.
When the light source 15 is lighted in this state, light of the light source 15 directly, or after being reflected by the reflector 14, makes characters and graduations on the dial 16 appear. The light is also directed to the pointer 10 through the light receiving opening portion 22 of the disk portion 20, and guided into the light emitting portion 32 by the light guide portion 34, thereby making the upper end of the light emitting portion 32 glow like a pointer.
The pointer 10 rotates in correlation to the rotation of a rotation shaft of the movement 13 in response to input signals and points to characters, graduations and so on according to values of the input signals. At this time, the light leakproof ring 17 prevents the outer region of the pointer 10 from glowing in the shape of a ring and lowering visibility.
As described above, the pointer suggested by the present applicant is lightweight and has high intensity, and the vehicular display device using the pointer can achieve a wide display of the pointer. Furthermore, since the pointer and the dial can be made to glow by the same light source, the production cost can be reduced, and a suitable blackfaced display device can be achieved.
Though the cost is thus reduced by using the light source common to the pointer and the dial in this vehicular display device, since the light source is made of an expensive ring-shaped cold-cathode tube, the cost is not always satisfactory.